1. Field of the Invention
The invention conceptually pertains to the control of engines, and relates to fuel control methods for multi-cylinder engines in which the amount of fuel that is supplied from fuel injection valves to a plurality of cylinders is controlled individually, fuel injection amount control methods, and engine operation state discrimination methods using the same, of an engine (particularly an engine with a supercharger) that controls an injection amount of fuel to be injected from the fuel injection valves, propulsion apparatuses for multiple engines in which propeller shafts are each individually connected to a plurality of engines, and crash astern fuel injection control methods for marine engines with a reduction and reversal device for abruptly stopping the ship when it is moving forward.
2. Description of the Related Art
Multi-cylinder engines such as diesel engines generally are furnished with an electric fuel injection apparatus that electrically controls fuel injection (that is, performs fuel injection amount control and injection timing control) according to the operation state of the engine in order to further improve its operability (for example, see Patent Document 1).
In such electric fuel injection apparatuses, the amount of fuel that is supplied from the fuel injection valves to the cylinders of the engine is individually controlled.
Such electric fuel injection apparatuses are conventionally known to include boost compensators that limit the fuel injection amount from the fuel injection valve in accordance with the amount of air that is sucked into the engine, so as to reduce the black smoke that is discharged from the engine (for example, see Patent Document 2).
The electric fuel injection apparatuses described above are used in engines furnished in marine vessels, for example. Conventionally, when a plurality of engines are installed in a marine vessel, for example, it is known that propeller shafts each having a screw propeller at one end are individually connected to the engines and a single regulator lever is used to synchronously adjust the revolution of the propeller shafts of the engines (for example, see Patent Document 3).
Further, in marine vessels, in general, an operation called a crash astern in which the clutch is switched from forward to reverse is performed to abruptly stop the marine vessel. When executing a crash astern, there is a risk that a load that is too large in magnitude will be applied to the engine and cause it to stall. This is because the actual revolution of the engine drops when the clutch is switched from forward to reverse. Thus, to prevent stalling, an engine revolution that functions as an engine stall limit is set for each magnitude of the actual revolution of the engine during execution of the crash astern, and when the speed falls below that engine revolution, the clutch is put into neutral to lower the burden on the engine and allow the actual revolution of the engine to recover, and once this has recovered to a certain degree, then the clutch is switched to reverse.
However, this method requires that the clutch is switched to reverse after the actual revolution of the engine has increased by a certain degree, and thus a considerable amount of time is necessary before the ship comes to a stop.
For this reason, conventionally, when a clutch astern is executed by switching the clutch from forward to reverse in order to stop the ship when it is traveling in the forward direction, control is performed so that the clutch hydraulic pressure is such that the engine does not stop due to the magnitude of the actual revolution of the engine, and this allows the moving ship to stop abruptly without stalling (for example, see Patent Document 4).
Patent Document 1: JP H4-59458B
Patent Document 2: JP 2001-227382A
Patent Document 3: JP 2001-128388A
Patent Document 4: JP 2001-71995A
However, in multi-cylinder engines furnished with a conventional electric fuel injection apparatus such as that illustrated in Patent Document 1, when, as shown in FIG. 21, it is not possible to supply fuel from the fuel injection valve to one of the six cylinders (in FIG. 21, the fourth cylinder), then, to ensure engine output, control is performed to increase the amount of fuel that is supplied from the fuel injection valve of the second cylinder, whose combustion cycle follows that of the fourth cylinder.
Control is, however, then performed to reduce the amount of fuel that is supplied from the fuel injection valve of the sixth cylinder, whose combustion cycle follows that of the second cylinder, by the amount that the supply of fuel from the fuel injection valve of the second cylinder has been increased, and thus the amount of fuel that is supplied from the fuel injection valve of the third cylinder, whose combustion cycle follows that of the sixth cylinder, is increased according to the amount that the supply of fuel from the fuel injection valve of the sixth cylinder has been reduced, and moreover the amount of fuel that is supplied from the fuel injection valve of the fifth cylinder, whose combustion cycle follows that of the third cylinder, is reduced according to the amount that the supply of fuel from the fuel injection valve of the third cylinder has been increased. This is because the amount that the crankshaft is rotated due to the supply of fuel from the fuel injection valve to each cylinder is determined after first recognizing that of the second cylinder, for example, which is before the combustion cycle of the cylinder in question.
The amount of fuel that is supplied from the fuel injection valves of the cylinders thus alternately increases and decreases and therefore is not uniform, and this results in vibration in the engine becoming quite large.
Further, in a conventional boost compensator such as that illustrated in Patent Document 2 above, the amount of intake air to the engine is detected by an intake air amount sensor or an intake pressure sensor (boost pressure sensor), and when the engine is in a transient state, such as when in a state of acceleration, the amount of fuel injected from the fuel injection valve is restricted based on the detection value detected by the sensor so as to inhibit the emission of black smoke while obtaining a good acceleration state.
In this case, when the sensor is broken, it is not possible to suitably restrict the amount of fuel that is injected from the fuel injection valve, and thus when the engine is in a transient state, the fuel injection amount necessarily increases and this results in the discharge of a large amount of black smoke from the engine.
Further, providing a sensor necessarily increases costs and thus is disadvantageous in terms of market strategy.
In this regard, there has been a need to inhibit the discharge of black smoke from the engine while obtaining a good acceleration state without depending on a sensor.
In a conventional example where a plurality of engines are installed in a marine vessel, such as illustrated in Patent Document 3 above, when the output of even one of the plurality of engines drops due to fuel injection problems relating to the fuel injection valve, there is a drop in the revolution of the propeller shaft of the engine whose output has fallen, and this causes a revolution difference with respect to the revolution of the propeller shafts of the other remaining engines. Here, conventionally the revolutions of the propeller shafts of the engines are synchronized by a single regulator lever, and thus it was not possible to synchronize the plurality of engines.
Further, as shown in Patent Document 4, when executing a crash astern in a conventional marine vessel, the clutch hydraulic pressure is controlled so that the engine due not stop due to the size of the actual revolution of the engine, and thus if the ship is moving at high speed and an accordingly large load is placed on the engine, it is necessary to change the pressure rise pattern of the clutch hydraulic pressure based on the ship speed, and the clutch hydraulic pressure cannot be stepped up until the ship speed drops to a speed where the load placed on the engine is small. For this reason, it is necessary to maintain a certain predetermined clutch hydraulic pressure until the ship speed has dropped by a certain amount, so that ultimately it takes time to stop a ship that is moving.
However, in the diesel engines that are adopted as the engines for marine vessels, the pressure of the supercharged air (boost pressure) is detected and control is performed to adjust the fuel injection amount with a boost compensator, and when the clutch is switched from forward to reverse when executing a crash astern, the boost is low at particularly low engine speeds and the amount of fuel that is injected to the engine is kept low by the boost compensator. In this case, as in the conventional example discussed above, when it is not possible to step up the clutch hydraulic pressure until the ship speed has dropped to a level at which the load placed on the engine is small, the fuel injection amount is kept low in conjunction with the drop in the actual revolution of the engine when executing the crash astern and the engine has a high likelihood of stalling, and it becomes necessary to adopt some type of countermeasure.
The present invention was arrived at in light of the foregoing matters, and it is an object thereof to provide a fuel control method for a multi-cylinder engine that allows the vibration in the engine to be actively reduced when the supply of fuel from the fuel injection valve to a certain cylinder of the plurality of cylinders has become impossible.
Another aspect of the invention was arrived at in light of the foregoing matters, and it is an object thereof to provide an engine fuel injection amount control method, and an engine operation state control method that employs the same, with which it is possible inhibit the discharge of black smoke from the engine while achieving a good state of acceleration, without depending on a sensor.
Another aspect of the invention was arrived at in light of the foregoing matters, and it is an object thereof to provide a propulsion apparatus for a plurality of engines with which, even if even one of the plurality of engines experiences a drop in output, it is possible to tune the other remaining engines with a single regulator lever.
A further aspect of the invention was arrived at in light of the foregoing matters, and it is an object thereof to provide a fuel injection control method during crash astern in a marine engine with a reduction and reversal device, with which it is possible to abruptly stop the ship while avoiding engine stalling due to control by the boost compensator or filtering during execution of the crash astern.